Coating composition



Patented June' Z I,

Y. mim oomosrrlon Frank w. port s.

Clair-ton, Pa, asslgnor to Pennsylvania Industrial Chemical Corporation,

a corporation of Pennsylvania No Drawing. Application Serial No.

November 17, 1934, 753,526

I (Cl- 1349-11) This invention relates to a coating compositionprimarily for the temporary protection of metallicsurfaces fromcorrosion.

It is desirable in all instances to protect the surface of metals .suchas the ferrous metals against corrosion between the period of the roughshaping of the metal and the final finishing treatment. Particularly inthe case of tubes, bars, sheets, andthe like, of steel which aresubjected which are to be subjected to a cold-rolling or cold? drawingoperation, a relatively great. length of time may intervene between theinitial shaping of the metal and the galvanizing or otherflnishingoperation. If during this period oftime the surface of the metal isexposed to corrosion, the pitting of the surface may well become such asis removable with difliculty by pickling, blasting, or other operationswhich may be performed preliminary to galvanizing-,colci-drawing,cold-rolling, or the like. The fact that the suriace of the shaped steelcarries mill-scale, expedites rusting, and intensifies the destructiveeffect of the rusting.

Aside from the difficulty encountered in eliminating rust and pitting,there is a substantial loss of metal due simply to the oxidation ofsurface metal into the form of rust. If metal sheets or bars, andparticularly sheets andstructural 0 shapes, be allowed to remainunprotected for the relatively extended period, which normallyintervenes between their initial shaping and their final treatment, theloss of metal due to rusting may amount to 6%, or more, of the initialweight of 35 the 11181351.

Frequently the rusting of the metal proceeds to such degree, that it isimpossible to clean the shape in suchmanner that it may be successfullygalvanized or otherwise permanently coated.

@ 'There is a loss, therefore, not only in metal destroyed by oxidation,and an increase in the labor necessary preparatory to galvanizing orother finishing treatment, but in extreme instances of rusting theentire preliminary work upon the 5 metal is lost and the shape must bescrapped.

- I am aware that variousmethods-have been, used temporarily to protect,the surface of sheets, bars, and the like, from, oxidation in the periodbetween the initial shaping of the metal and the galvanizing, or otherfinishing, treatment to which the shape is to be'subjected. Priormethods of protecting the surface of the metal consist in painting,varnishing, lacquering, or phosphating, the surface. Of these, all savethe phosphating process, necessitate removal by an alkali treatto agalvanizing, or other coating, treatment, or

ment, .or solvent. treatment, before the stock may besubjected to theapplication of a permanent coating, or other finishing treatment. Analkali treatment, or a solvent treatment, is a definitely added step inthe treatment of the stock, and g as such, increases production costs.

The oxidation of paints, varnishes, lacquers, and the like, on thesurface of the metal, occurring during the period between theapplication of such temporary protective coating and its re- 10 moval,renders its complete removal so diflicult that there frequently remainon the surface of the metal, after a removal treatment, areas stillcarrying a deposit of the coating composition, or some of lts'constituents. Such coated areas, of is courseydetract substantially fromthe complete- .ness and value of the galvanizing treatment, since anybreak in the close adhesion of a galvanized coating tends to the rapiddestruction of the metal presumably protected by the coating.

The phosphate process, utilizing generally a manganese phosphate," actsto produce by reaction with the metal to be protected a relatively thinlayer of ferric phosphate. This layer must be laboriously removed priorto galvanizing or plat- 25 ing, since its presence on the metal preventsgood galvanization of the stock.

It is, of course, necessary in order that a temporary coating be ofvalue that it should not be freely soluble in water, and that it shouldnot, to any great degree, hydrolyze. I have solved the problem both ofprotection for the metal, and removal of the coating, by producing acoating which is insoluble in water, and which does not hydrolyzereadily; but which is readily removed 5 by highly dilute solutions ofthe mineral acids.

It is well-known that, .as various stock comes from a hot mill, itinevitably carries asubstantial amount of scale, which scale has beenreferred to above as increasing the tendency toward rusting of thestock. It is the usual practice to subject the. stock, whether it be inthe form of bars of any cross-sectional contour, tubes, sheets,orplates, to a pickling bath before the shaped metal is coatedpermanently by galvanizing or the application of some other protectivecoating, or before it is subjected to a finishing treatment such ascold-rolling orIcold-drawing.

The composition of a'pickling bath, as used in the steel industry, is asolution of sulphuric acid,

usually a seven per cent. solution, used at a temperature of about 150.F. It should be. emphasized that the pickling of the shaped ferrousmetal in a'bath of this nature is 'not'only a well-known,- butsubstantially an inevitable, step in the production of line finishedstock. My coating is of such nature that it is wholly removed during thenormal pickling of the metal to which it has been applied. It mayfurther be noted that my coating is removed so rapidly in the picklingbath that it does not add substantiallyto the duration of the picklingtreatment for the removal of scale.

The fundamental ingredient of my coating composition is a productobtained from the reaction of a metallic compound with an organic sameacidic relation as do the phenols.

chemical containing the hydroxyl (OH) radical, which is an acidicaromatic compound of either the phenol, or phenolic,'series. It can bestated generally that practically all members of the phenol, andphenolic, series are suitable for my purpose. The type of metalliccompound should desirably be such as will react with the acidic'aromatic under practical reactive conditions.

Since the phenol and phenolic compounds are of relativelyweak acidity,the metallic compound should desirably be of the more readilydecomposable type such as the oxide, hydroxide, or carbonate, of themetal. Certain organic salts of the metals, such as the acetates, maywith advantage be used for my purpose.

The theory of my invention is to produce a product either ofsubstitution, or addition, with the phenol, or phenolic, compound, whichproduct possesses certain resin-like qualities rendering it suitable foruse as the film-forming ingredient of a temporary coating composition.

Among the aromatic acids, there is a type of acid in which the acidichydroxyl (OH) radical is attached to a carbon atom to which no atom ofoxygen, other than that comprised in the hydroxyl is attached. These areknown as phenols,

'whether they contain one, or more, hydroxyls.

For example, the cresols, or cresylic acids, are phenols, as are thexylenols and the specifically named phenols. I The naphthols, in whichthe naphthalene double ring replaces the benzene ring, are also phenols.These all, as stated, are suitable for my purpose. I

I may also use as the organic basis of my compound, one of the phenolicacids. These are aromony in the electromotive series need positivelybeeliminated. This is primarily because of the fact that they arerelatively so inert. It is a fact,

however, that the highest member of the electromotive series cannotdesirably be utilized to react with a phenol, or phenolic acid, toproduce a 111mi'orming ingredient for my coating composition. Thecompounds produced by reaction of a phenol,

or'phenolic acid, with potassium, sodium, or the theoretical metalammonium are quite soluble in water, and would, therefore, give butevanescent protection against oxidation of a metallic surface. Barium,strontium. and calcium, tend to produce products of addition, ratherthan substitution, with the phenols and phenolic acids. The compoundsobtained by reaction with them are, therefore, of high melting-point.Such compounds are also somewhat soluble in hot water.

The products of reaction of these metals with a, phenol, or phenolicacid, may suitably be used in admixture with a product of reactionbetween a phenol, or phenolic acid, and one of the metals lower in theelectromotive series than calcium. Thus, I have used, as a film-formingmass, a mixture of calcium cresylate and lead naphtholate. It isprobable that reaction products of the phenols, and phenolic acids, withbarium or strontium might similarly be used.-

It is preferable to use, for reaction with a phenol, or phenolic acid, acompound of one of he metals lower in the electromotive series than iscalcium, if the aromatic compound of such metal is to be used alone as afilm-forming ingredient. Of the metals lower than calcium, however, itshould be noted that the compoundsof zinc and magnesium haveapproximately thesolubility of calcium. The reaction product of thesemetals, therefore, is preferably not used byitself save when the productresults from the reaction of zinc, or magnesium, with one of the organicreagents of higher molecular weight, such as naphe thol, or a phenolicmixture in which the higher molecular weight reagent, such as naphthol,predominates.

For use in the temporary protection of ferrous metal from, rusting, Ifind that a highly reactive lead compound gives ideal results. This isfor the reason that in a pickle bath one product of reaction between theorganic lead compound and the sulphuric acid of the bath is theinsoluble lead sulphate, which, being heavy, falls to the bottom of thebath. Antimony sulphate is unstable, and acts to regenerate sulphuricacid and to produce the insoluble, but flocculent, hydroxide of themetal. Care must be taken in its use to prevent adherence of thisprecipitate to the surface of the metal which has been pickled to aclean,

bright, condition. The same is true of tin.

Returning to the organic constituent of my material, phenol, cresol,xylenol, naphthol, and sellicylic acid .are among the organic substanceswhich I have used,jas is also 'amyl-phenol (parateritary-amyl-phenol).Broadly considered, the organic constituent of my material may beselected from any of the hydroxy-aromatic hydrocarbon compounds 01' thephenolic type, whether or not they contain other'substituents, such ascarboxyl groups. They all respond to the type structure X-.R-OHb; inwhich X is a hydrocarbon or carboxyl, a is zero or a whole number, R isan 'aryl group of one or more benzene nuclei, OH is an hydroxyl, and bis a whole number.

The reaction product of lead oxide with phenol has the disadvantage thatit is somewhat susceptible to hydrolysis, and to a lesser extent thereaction product with cresol is susceptible to hydrolysis. Leadcompounds of xylenol and naphthol have practically no tendency tohydrolyze. Naphthol has a melting-point so high that it tends to lessenthe adhesive qualities of the compound, produced by its reaction withthe metal. A combination of cresol and naphthol is wholly satisfactory,since the inclusion of naphthol decreases the tendency of the combinedchemicals to hydrolyze to a point at which such tendency is notpractically disadvantageous, while the combined melting-point issufliciently lower than the melting-point of the naphthol compound 4 tosecure good adhesion.

It may be generally stated that among the stated organic compounds andtheir l omologues,

suitable combinations may readily be made to out conducting any extendedseries of experimerits. As a guide, it may be stated that by using asthe organic constituent of my material 60% by weight of naphthol to 40%by weight of cresol, I have. obtained by reaction with lead oxide afilm-forming material which in, use, as hereafter described, whollyprotected a ferrous surface to which it was applied for a period inexcess of three months, without any appreciable deterioration occurringfrom hydrolysis, although the coated metal was stored in a locationexposed to moisture. I As a typical example of the production of theorganic-metal compound, a mixture of cresol and naphthol was fused, andlead oxide was introduced slowly in solid state, and divided form, withagitation. Throughout the reaction the temperature was maintainedadequate rapidly todrive off water evolved by the reaction, and wasmaintained below that point at of the organic reagents would occur. Inthis reaction I have found a temperature of approximately 320 F.suitable, and have maintained such approximate temperature throughoutthe valency, since the some tendency to hydrolyze, if the actualconreaction. I I A v r It should be explained that thelead oxide, orother metal compound, desirably is not included to the full amount basedon its combining weight and valency. This is for the reason that, ifin-" cluded up to the full amoun the resulting product' is of lessenedsolubility in hydrocarbon solvents. It is desirable that the lead oxideshould be included in a percentage not substantially on its combiningweight and less than 90% based resultant product exhibits tent of themetal is substantially less than 90% of the theoretically completereaction between it and the organic chemicals. I have found that aninclusion of lead oxide ina quantity equal to 95%, its theoreticalcombining weight and valency, is suitable. Formula: for the reaction maybe given as follows:-

(A) Cresol and lead giving "lead cresylate and water 7 2CeH-iCH3OH+PbO-(CcHiCHsO) aPb-i-HaO (B) Cresol and. lead giving additive compound2CsH4CHaOH+PbO- (C6H4CH3OH) 2 P130 (C) Naphthol and lead giving "leadnaphtholate and water I (Dl Naphthol and lead giving additive compound Iam certain-that a large proportion of the reaction occurs in accordancewith formulieA and C. This is because of my observation of a relativelygreat quantity of evolved water, which proved to be approximately of thetheoretical water product of the reactions. available literature as tothis type of reactio'n.

Although the exact nature of the reaction is theoretical, I am led, asmentioned above, to the belief that it is substantially wholly inaccordance with the formula: A and C. As noted above. in

which volatiliz ation ,quately protects the metal for a formingmaterial, as of a lead compound phenols, or phenolic acids, decomposesto produce by reaction with the sulphuric acid of the pickling There isno tion of the lead sulphate.

reacting a calcium compound with-a phenol,

or phenolic acid, the tendency, is to produce to a 'of mineral acids,even in relatively high dilution. .This material is soluble in the usualcoal tar distillate solvents and in mixed coal tar and petroleumdistillate solvents.

I have made up various grades of my coating composition by dissolvingvarious specimens of my special-film-forming material in mixed solventfrom a proportion of 20% by weight of the film-forming materialto 60% byweight of the film-forming material. The latter proportion is, for thespecific material formed in the above example, the maximum content offilm-forming material in the solvent which gives a fiowable composition.I have found that a coating composition comprising 35% by weight of myspecial film forming material and 65% by weight of a combined mixedsolvent, when spread upon the surface of steel as shaped in a .hot mill,adeperiod of at least three months.

The solution of my special film-forming ma terial may be made ofcold-cutting, if so desired. It is convenient, however, rial in thesolvents, immediately upon completion of the reaction between theorganic reagents and the metallic compound used, as evidenced bycessation in the evolution of water from the reaction mixture. Thecoating compoof the nature above-mentioned, it has been found that thetemporary coating is removed in from 1 to 3 minutes after theintroduction of the metal,

exposing the surface of the metal to the action of the pickle forbrightening of the metal in accordance with the usual functioning of apickle bath. There re-- mains on the metal after pickling no trace ofthe coating composition.

.It has been above noted that my special filmproduced by the reactionwith one or more of the bath an insolublelead sulphate, and that thisinsoluble product of the reaction of the pickling the bottom ofthepickle bath is precipitated to vessel as is also, in substance, theorganic component, or components.

In explanation, it may be mentioned that, in accordance with theformulae, which I consider the more accurate as illustrating thechemical composition of ingredients in my special filmforming mass, theacidic aromatics are reformed by reaction with the sulphuric acid, inthe forma- This may be illustrated by the following formula relating tothe reaction of leaded naphthol with sulphuric acid:

The same is true of the removal of mill-scale and,

to dissolve the matedipping, brushing,

While most of the organic acid is precipitated,

as explained above, a relatively small percentage bath. It should beemphasized that the protection of; the surface of a highly corrosionalmetal, such as steel, in the intervening period between its shaping andpickling, is of great importance. By protecting the surface of the metalduring this period, and thus preventing the'formation of rust, asmoother plating with metals such as tin,

, chromium, and the like, is obtained, since progressive pitting of themetal is prevented. A

galvanized surface of the metal is also smoother, when permanentlyprotectedby galvanizing, due to the absence of deep pitting, and thelike, and when hot galvanized, the galvanized coating is brighter andmore uniform, showing a clear spangle. Due to the absence of surfacedefects, .a more uniform and homogeneous permanent coating may beapplied to the metal, whether it be galvanized, or whether it be platedwith any of the protective metals.

With these advantages, arising from the temporary protection of steelsurfaces prior to the application of a permanent protective coating, in

, mind, it should be appreciated'that my coating composition hasrendered such protection feasible commercially. Previous coatings beingeither so soluble, or so subject to hydrolysis that they wereineflicient, or of such, nature as to render their removal difficult anduncertain, it has been preferred to permit rust to form upon the steelrather than to protect it by a paint or varnish. -My coatingcomposition, since it both gives adequate protection and is readilyremovable, presents no problems which might inhibit its universal use.It is to be noted that the only added step, in the treatment of themetal, involved in the use of my coating, is the mere application of thecoating, since its removal occurs in a step normally incident in thetreatment of steel.

Incidentally, it may be noted that my coating composition issubstantially colorless, and that it will retain the color of the usualpigments. It may thus be colored in accordance with the stock to whichit has been applied, either to identify a customer to whom the stock isto be delivered, or for any other p pose of identification orclassification. r

. Also the pigmented composition may, if desired, be used on stock, notnecessarily protected from corrosion, by applying it simply'as a paintor stencil composition to give identification of the stock as to origin,grade, shipment, or the like. As so used, the ready removability of thecomposition in a pickling bath is similarly of great advantage. I

I It should be explained that by reacting a compound of any one or moreof the metals, in accordance with the explanation and limitations abovegiven, with any oneor more of the phenols, such as phenol, cresol,xylenol, or naphthol, -a compound is obtained which is sufficientlyinsoluble in water to give temporary protection to a surface for someperiod of time and under some conditions. The same is true as tocompounds of one or more of the metals with the homologues of phenol,cresol, xylenol, and naphthol, and with the phenolic'acids; I

In the specification, I- havepreviously disclosed factors which enableone skilled in the art to produce most readily and economically thevariants of my temporary coating composition suitable and adequate forvarious conditions of use. In making such detailed disclosure it hasnot-been my intention to limit the invention, to any special metalliccompound or compounds, or to any special organic acid or acids,responding to the definition of a phenol or phenolic acid. A chemistskilledin the art will, as noted above, be able to use to advantage forthe protection of metal or some other material, for some period of time,each of the compounds considered by me as workable. Such description aspoints out the tendency of certain of the compounds to hydrolyze, forexample, is not intended herein as excluding such compounds fromconsideration in a protective cgatingforany purpose, but suchdescription is to be considered as instruction to the art as to thepractical advantages and limitations of the several of the possiblecompounds, thus giving a guide to the art, which permits optimumadvantage to be obtained from my invention.

Thus, I have in the foregoing specification criticized phenol, as theorganic chemical to be reacted with a metallic compound, for the reasonthat itis relatively subject to hydrolysis. This acid may, however, bereacted with a metallic compound to protect a surface for a relativelyshort period of time. The like is true of cresol as reacted alone with ametallic compound. In the specification I have criticized xylenolandnaphthol, as producing by reaction with a me tallic compound, a productwhich is deficient in adhesion. None the less, a mass obtained byreactionwith these latter phenols, may be used upon surfaces of a natureto facilitate the adhesion of a coating. As applied to surfaces otherthan metallic surfaces, the possession of adhesive qualities in lesserdegree may work no disadvantage.

Similarly I have stated that the more reactive compounds of the metalsshould desirably be used, because of the relatively weak acidity'of thephenols and phenolic acids. By this I do not intend to state that other,less reactive, comcompounds may be used, either by themselves or inassociation with other metallic compounds, to

make variants of my coating composition that,

with the guides comprised in the specification,

it becomes wholly proper to utilize in the claims, as defining mycoating composition generally, the term metal compound.

I claim as my invention:

1. A temporary coating composition for the rust protection of metallicbodies consisting essentially of a resin-like compound capable offorming a hard adherent film on metallic surfaces, which compound is thereaction product of at least one hydroxy-aromatic compound of thephenolic type with at least one metal selectedfrom amongst the group ofmetals consisting of and embraced between calcium and bismuth; in theelectromotive series, and evaporative solvent in quantity adequate torender the composition fiowable; in the composition the resin-likefilmforming material being readily decomposable upon subjection tomineral acids in the order of dilution in which they arepresent in.pickling baths 2,121,475 I it for steel, and the non-volatile content ofthe composition being substantially free of any coherent materialcapable of resisting decomposition upon subjection to mineral acidsoithatorder of "dilution.

2. A temporarycoating composition for the rust protection of metallicbodies consisting essentially of a resin-like compound capable offorming a hard adherent film on metallic surfaces,

'10 which compound is the reaction product'of lead witha mixed organicreagent consisting of cresol and naphthol, and evaporative solvent inquantity adequate to render the 'compositionfiowable; in the compositiontheresin-like film-forming material being readily decomposable uponsubjection to mineral acids in the order of, dilution in which they arepresent in pickling baths for steel, and the non-volatile content of thecomposition being substantially free of any coherentmaterial calorpableof resisting decomposition upon subjection to mineral acids of thatorder of dilution;

3. A temporary coating composition-for the rust protection. ofmetallicbodies consisting essentially of a resin-like material capable offorming a hard adherent film on metallic surfaces, which is a leadcompound of a least one hydroxy-aroriiatic hydrocarbon compound of thephenolic type with at least one metal selected from the metals includingand embraced by calcium and bismuth in the electromotive series, andvolatile dilution in f solvent i n'quantity adequate to render thecompo- 'sition flowable; in the composition the resin-like film-formingmaterial being readily decomposable upon subjection to mineral acids inthe order of which they are presentin pickling baths'for steel, and thenon-volatile content of the composition being substantially free of anycoherent material capa 1c of resisting decomposition uponsubjection tomineral acids of that 40 order of dilution.

4. A temporary coating rust protection of sentially of a resin-likematerial capable of forming a hard adherent film on metallic surfaces,and

consisting of at least one metal compoundprocoherent material 0 tionupon subjection to miner 5 of dilution.

duced by reaction of a mixed organic reagent consisting of more than onehydroxy-aromatic hydrocarbon compound of 'the phenolic type with atleast one metal selected from the metals ino cluding and embraced bycalcium and bismuth in the electromotlve series and volatile solvent inquantity adequ' te to render the. composition flowable; in thecomposition the resin-like flimforming material being readilydecomposable upon subjection to mineral acids in the order of dilutionin which they are present in pickling baths for steel, and thenon-volatile content of the compositionbeing substantially freeoi anycapable of resisting decomposii acids of that order 5. A temporarycoating composition-for the rust protection of metallic bodiesconsisting essentially of a resin-like organic compound of the metalzinc capable of forming a hard adherent film on metallic surfaces, saidcompoundpbeing the said metal with a the reaction product ofhydroxy-aromatic hydrocarbon phenolic type reagent having a molecularweight higher than that of cres'ol and consisting of at least onehYdl'OXY: aromatic hydrocarbon compound of the phenolic type, andvolatile solventin quantity adequate to render the composition flowable;

in the composition the resin-like film-forming material being readilydecomposable upon subjection to mineral acids in the order of dilutionin which theyare present in pickling baths for steel, and thenonvolatilecontent of the stantially free of any coherent'material capable ofresisting decomposition upon subjection to mineral acids of that orderof dilution.

6. Av temporary coating composition for the rust protection of metallicbodies consisting essentially of a resin-like organic compound of themetal magnesium capable of forming a hard adherent film on metallicsurfaces, said compound being the reaction product of the said herentmaterial capable tion upon subjection to-mineral acids ofthat order ofdilution.

'7. A temporary coating rust protection of metallic bodies consistingessentially of a resin-like material consisting of lead compounds ofmore than one hydroxy-arm matic hydrocarbon phenolic type compound ca- 1pable of forming a hard adherent film on metallic surfaces, the saidhydroxy-aromatic hydrocarbon compounds of the phenolic type differing intheir molecular weight, and volatile solvent in quantity adequate torender the 'composition'flowable; in the composition the. resin-likefilm-forming material being readily decomposable upon subjection tomineral steel, and the non-volatilecontent .of the composition beingsubstantially free of any coherent material capable of resistingdecomposition upon subjection to mineral acids of that order ofdilution. y

FRANK W; CORKERYl composition being subcomposition for the non-volatilecontent of the composition being substantially free of any ccofresisting deoomposi--

